Invading a country that did not attack us was wrong. There were better ways to prevent Saddam Hussein from becoming a threat than storming into his country and killing the citizens of that country. See e.g. An Alternative to War for Defeating Saddam Hussein The invasion was immoral. It was a sin.
There is a price to be paid for this sin. And the question is simply one of how we will pay that price.
OPTION 1: We send hundreds of thousands of Americans to Iraq to actual secure the country while we spend billions of dollars to rebuild the infrastructure and create an economy there. We lose many Americans in attacks in Iraq in the meantime.
OPTION 2: We leave. The country that has become the ideal breeding ground for America haters produces a whole new crop of anti-American groups. We suffer several terrorist attacks over many years. We witness the death of many, many innocent Iraqis.
OPTION 3: We continue to ineffectually occupy Iraq, breeding even more hatred. We continue to lose American lives in the meantime. We suffer terrorist attacks once these group of America hater get organized. (Maybe slowed while we're there, maybe not.) Then we go to OPTION 2 after we grow tired of OPTION 3.
This is the fact of life reflected in the notion of a vengeful god. There is nothing we can do to avoid the consequences of this sin. I personally wish we could do OPTION 1. However, we don't seem to have the will for it.
Speaking of Abraham Lincoln, this is how he reflected on another national sin and the consequence of that sin:
Yet, if God wills that it continue until all the wealth piled by the bondsman's two hundred and fifty years of unrequited toil shall be sunk, and until every drop of blood drawn with the lash shall be paid by another drawn with the sword, as was said three thousand years ago, so still it must be said "the judgments of the Lord are true and righteous altogether."
Abraham Lincoln's Second Inaugural Address.